Cold shields are often incorporated into heat-seeking missiles and other such components to shield the detector from unwanted stray light transmissions. The cold shield allows the detector to “see” light and infrared radiation from optical surfaces within the imaging path defined by the cold shield's field of view while preventing the viewing of warm optical surfaces outside that field of view. By reducing stray light—i.e., light illuminating the detector that has not followed the imaging path—detector sensitivity and overall heat-seeking performance can be improved.
Stray light can be characterized by the number of ghost reflections or scatter interactions that occur before the light reaches the detector. Zero-order paths are the brightest stray light paths and travel straight to the detector without any scatter interactions. First-order paths scatter once before reaching the detector; second-order paths scatter twice, and so on. Higher order paths are generally of less concern as their effective energy has been reduced, and consequently cold shields primarily focus on reducing zero and first-order paths.
Known cold shields are unsatisfactory in a number of respects. For example, typical shields continued to include surfaces oriented to reflect light into the detector from various interior surfaces. Similarly, the placement and shape of curved surfaces within typical shields are often non-optimal with respect to reducing first-order scattering. Furthermore, as many cold shields are fabricated using multiple components, the internal blunt and rounded edges between such components are generally large and present a significant source of unpredictable scattering.
Accordingly, it is desirable to provide cold shields that are manufacturable and reduce stray light transmission. Other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.